This invention relates to high energy density electrical capacitors.
In typical wound capacitors with electrodes made of solid metal foils, damage to the dielectric system during manufacture (resulting from, e.g., local imperfections in the dielectric, irregularities in the electrodes, or foreign particles) may cause the capacitor to break down when energized, rendering it unusable.
So-called self-clearing capacitors use metallized electrodes, each composed of a dielectric backing (e.g., paper or polypropylene), coated with a thin metal layer. When an appropriate voltage is applied, the metal is vaporized or converted to a nonconductive metal oxide at points were defects exist. Conduction through the dielectric is thereby eliminated at damaged places, rendering the capacitor usable.
The thin metal coating of metallized electrodes is delicate and easily detached from or vaporized along the line of contact with the solid metal terminals of the capacitor, thus limiting the current capacity of the capacitor.